Heating and Cooling Unit with Semiconductor Device and Heat Pipe

ABSTRACT

Aspects of the invention support the changing of a serving surface temperature in order to cool or heat the serving surface. Heat is transferred to or from the serving surface through at least one Peltier device, a heat pipe, and a heat sink. The mode of operation is determined by changing the electrical power polarity to the at least one Peltier device. A control device may activate the at least one Peltier device from a measured temperature and a temperature setting with a hysteresis. A plurality of Peltier devices may be partitioned into different subsets so that the control device may activate a selected subset during different time intervals. When the measured temperature is outside a temperature range, all of the Peltier devices may be activated, while only a selected subset may be activated when the measured temperature is within the temperature range and until a hysteresis temperature is reached.

TECHNICAL FIELD

Aspects of the disclosure relate to a hot/cold unit for heating and/or cooling an item on a serving surface. In particular, the hot/cold unit uses a semiconductor device, such as a Peltier device, and a heat pipe.

BACKGROUND

Perishable foods for home, market, catering and restaurant buffets are conventionally chilled by ice or commercially manufactured containers of freezable material, or by refrigeration systems. When the ice melts and the freezable material warms, these cooling media lose their ability to keep foods safe and may render them unsuitable or hazardous for consumption. Refrigeration systems are bulky and costly, requiring condensers, coils and harmful chemicals and, further, must be serviced and maintained. Additionally, they are not easily adapted for portability.

Other foods need to be heated or kept warm for home, market, catering and restaurant buffet service. Conventional sources of heat include flame and electricity, e.g. by use of alcohol-based combustible gels or by electric hot plates. Flame sources often produce local hot spots and uneven heating and may produce fumes, odors, or other combustion products. The indoor pollution and health risks to food service workers and patrons from these combustion products may be viewed with concern by those in the industry.

In the presentation of food and/or beverages such as for a buffet service, it is often desirable to store, transport, and/or present the buffet items in a convenient, presentable fashion. It is often further desirable to provide the items either above or below the ambient temperature of the presentation environment. Moreover, in-home hosting has trended upward, and could benefit from equipment improvement. Further, the costs and convenience of improved buffet service, storage, transportation, and/or presentation means may be improved such that they are more accessible and feasible in the market place.

While traditional servers for heating and/or cooling may not require fuel or ice to achieve a desired temperature of an item, traditional servers may rely on a temperature adjusting element in conjunction with an active exchange device, e.g., a liquid circulation pump, to facilitate energy transfer and thus mitigating the temperature of the temperature adjusting element. This approach may generate noise may typically increases the cost of the traditional server.

SUMMARY

An aspect of the invention provides apparatuses, computer-readable media, and methods for changing the temperature of a serving surface in order to cool or heat an item on the serving surface. Heat is transferred to or from the serving surface through a semiconductor device (e.g., a Peltier device), a heat pipe and a heat sink.

With another aspect of the invention, an apparatus for reducing the temperature of a serving surface includes at least one Peltier device that transfers heat from the serving surface to a heat pipe to a heat exchange device. Alternatively, the apparatus may increase the temperature of the serving surface by reversing the operation of the at least one Peltier device.

With another aspect of the invention, a control device activates the at least one Peltier device from a measured temperature of the serving surface and a temperature setting. The control device activates the at least one Peltier device in order change the serving surface according to the temperature setting. Moreover, hysteresis may be incorporated so that control cycling of the at least one Peltier device may be reduced.

With another aspect of the invention, a plurality of Peltier devices may be partitioned into different subsets so that the control device may activate different subsets during different time intervals. When the measured temperature of the serving surface is outside a temperature range, all of the Peltier devices may be activated, while only a selected subset may be activated when the measured temperature is within the temperature range and until a hysteresis temperature is reached.

Various aspects described herein may be embodied as a method, an apparatus, or as one or more computer-readable media storing computer-executable instructions. Accordingly, those aspects may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Any and/or all of the method steps described herein may be implemented as computer-readable instructions stored on a computer-readable medium, such as a non-transitory computer-readable medium. In addition, various signals representing data or events as described herein may be transferred between a source and a destination in the form of light and/or electromagnetic waves traveling through signal-conducting media such as metal wires, optical fibers, and/or wireless transmission media (e.g., air and/or space).

Aspects of the disclosure have been described in terms of illustrative embodiments thereof. Numerous other embodiments, modifications, and variations within the scope and spirit of the disclosure will occur to persons of ordinary skill in the art from a review of this disclosure. For example, one of ordinary skill in the art will appreciate that the steps illustrated herein may be performed in other than the recited order, and that one or more steps illustrated may be optional in accordance with aspects of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention and the advantages thereof may be acquired by referring to the following description in consideration of the accompanying drawings, in which like reference numbers indicate like features and wherein:

FIG. 1 shows a block diagram of a serving apparatus operating in a cooling mode in accordance with an embodiment of the invention.

FIG. 2 shows a block diagram of a serving apparatus operating in a heating mode in accordance with an embodiment of the invention.

FIG. 3 shows a Peltier device in accordance with an embodiment of the invention.

FIG. 4 shows a heat pipe in accordance with an embodiment of the invention.

FIG. 5 shows a serving apparatus in accordance with an embodiment of the invention.

FIG. 6 shows a control device in accordance with an embodiment of the invention.

FIG. 7 shows circuitry for controlling Peltier devices in accordance with an embodiment of the invention.

FIG. 8 shows an arrangement of Peltier devices for changing a serving surface temperature in accordance with an embodiment of the invention.

FIG. 9 shows an arrangement of Peltier devices for changing a serving surface in accordance with an embodiment of the invention.

FIG. 10 shows a flowchart for controlling a serving apparatus in accordance with an embodiment.

FIG. 11 shows a flowchart for controlling Peltier devices in accordance with an embodiment.

FIG. 12 shows a flowchart for controlling Peltier devices in accordance with an embodiment.

DETAILED DESCRIPTION

In the following description of the various embodiments, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration various embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural and functional modifications may be made without departing from the scope of the present invention.

FIG. 1 shows a block diagram 100 of a serving apparatus operating in a cooling mode in accordance with an embodiment of the invention. Block diagram 100 shows the basic elements of the serving apparatus but may not explicitly show the dimensions and relative placement of the elements. For example, heat pipes 105 and 104 may be bent in a horizontal plane rather than a vertical plane so that the operation of the heat pipes is not adversely affected (e.g., by gravity).

The measured temperature of serving surface 101 is changed by transferring heat from Peltier devices 102 and 103 through heat pipes 104 and 105 and through heat sinks 106 and 107, respectively.

Control device 108 activates and deactivates Peltier devices 102 and 103 based on an indication from temperature sensor 109 that is indicative of the measured temperature of serving surface 101. Temperature sensor 109 is typically placed against serving surface 101 in order to provide thermal coupling. For example, when the measured temperature is above a cooling temperature setting (i.e., the desired temperature) control device 108 provides electrical power to Peltier devices 102 and 103 through electrical connections 110 and 111 and connections 112 and 113, respectively.

With some embodiments, heat transfer may be enhanced by fans 114 and 115 producing air circulation from heat sinks 106 and 107, respectively, and through vent openings 116 and 117, respectively.

FIG. 2 shows a block diagram 200 of a serving apparatus operating in a heating mode in accordance with an embodiment of the invention. With some embodiments, the serving apparatus may be the same serving apparatus as with block diagram 100.

Control device 208 reverses the transfer of heat with respect to block diagram 100 by reversing the electrical polarity of electrical connections 210 and 211 and connections 212 and 213. (As will be discussed, the Peltier effect is a reversible process.) Consequently, heat flows to serving surface 201 to heat it.

FIG. 3 shows Peltier device 300 in accordance with an embodiment of the invention. However, some embodiments may use other types of semiconductor devices that provide similar heating and/or cooling characteristics. Heat is transferred between top side 351 and bottom side 352 based on the Peltier effect. Thermoelectric cooling by Peltier device 300 uses the Peltier effect to create a heat flux between the junctions of two different types of materials. Peltier device 300 may be classified as a heat pump. When direct current is provided to Peltier device 300, heat is moved from one side to the other. Peltier device 300 may be used either for heating or for cooling since the Peltier effect is reversible. For example, heat may be transferred from top side 351 to bottom side 352 to cool a serving surface by providing electrical power at terminals 314 and 315. Moreover, the direction of the heat transfer may be reversed (i.e., from bottom side 352 to top side 351) in order to heat the serving surface by reversing the polarity of the electrical power at terminals 314 and 315.

Peltier device 300 comprises a plurality of N type and P type semiconductor grains 301-309 that are electrically interconnected through electrical conductor arrangements 310 and 311. Ceramic layers 312 and 313 provide thermal conductivity as well as electrical isolation so that Peltier device 300 is able to cool or heat a serving surface. With some embodiments, the serving surface and heat pipe are thermally coupled to ceramic layers 312 and 313, respectively.

With some embodiments, one or more Peltier devices may be used to exchange heat with the serving surface. For example, with the embodiment shown in FIG. 5, four Peltier devices may provide faster cooling than with one Peltier device. Additional Peltier devices may be used; however, electrical power and physical constraints may be factors that limit the number of Peltier devices.

FIG. 4 shows heat pipe 400 in accordance with an embodiment of the invention. With some embodiments, heat pipe 400 is a heat-transfer device that combines the principles of both thermal conductivity and phase transition to efficiently manage the transfer of heat between two solid interfaces. At the hot interface within heat pipe 400, which is typically at a very low pressure, a liquid (fluid) is in contact with a thermally conductive solid surface that turns into a vapor by absorbing heat from the surface. The vapor condenses back into a liquid at the cold interface, releasing the latent heat. The liquid then returns to the hot interface through either capillary action or gravity action, where it evaporates once more and repeats the cycle. In addition, the internal pressure of the heat pipe may be set or adjusted to facilitate the phase change depending on the demands of the working conditions of the thermally managed system. With some embodiments, heat pipe 400 does not contain mechanical moving parts and typically requires little or no maintenance.

Heat pipe 400 may be a heat-transfer device that combines the principles of both thermal conductivity and phase transition to efficiently manage the transfer of heat between two ends. With traditional systems, a radiator using single-phase convection with a high-speed motor often provides heat transfer. However, heat pipe 400 can transfer the heat efficiently without a high-speed motor.

Heat pipe 400 transports heat from portion 452 to portion 451. Heat pipe 400 comprises casing 401, wick 402, and vapor cavity 403. Casing 401 may comprise a sealed pipe or tube made of a material with high thermal conductivity such as copper or aluminum at both hot and cold ends. Working fluid evaporates to vapor absorbing thermal energy at event 404. Examples of such fluids include water, ethanol, acetone, sodium, or mercury. The vapor migrates along cavity 403 from portion 452 (high temperature end) to portion 451 (low temperature end). The vapor condenses back to fluid and is absorbed by wick 402 at event 406, and the fluid flows back to portion 402 through wick 402.

With some embodiments, referring to FIG. 5, heat pipe 503 comprises a sealed pipe or tube made of a material with high thermal conductivity, i.e., copper at both hot and cold ends. For example, a copper pipe or tube may be approximately 300 MM long with a diameter of approximately 8 mm. Heat pipe 503 is typically constructed with a tube shell, wick and end caps. Heat pipe 503 may be drawn into negative pressure and may be filled with the fluid such as pure water. Wick 402 is typically constructed with a capillary porous material. Evaporation of the fluid occurs at one end of heat pipe 503, while condensation occurs at the other end. When the evaporation end is heated, the capillary action in the fluid evaporates quickly. With a small gravity difference between two ends, the vapor flows to the other end, releasing heat. The vapor is then re-condensed into fluid, which runs along the porous material by capillary forces back into the evaporation end. This cycle is repeated to transfer the heat from the one end to the other end of heat pipe 503. This cycle is typically fast, and the heat conduction is continuous. Good performance of the wick is often characterized by:

-   -   1. Large capillary action or small effective aperture of wick,     -   2. Smaller fluid flow resistance, which have higher         permeability,     -   3. Good thermal conductivity characteristics, and     -   4. Good repeatability and reliability in the manufacturing         process.

Referring to FIG. 4, heat pipe 400 may have bends in order to route the heat transfer to or from a heat exchange device providing that the bends to not adversely affect the capillary or gravity action of heat pipe 400. For example, referring to FIG. 5, heat pipe 503 is bent in a horizontal plane to route the heat between Peltier device 502 and heat sink 505.

FIG. 5 shows serving apparatus 500 in accordance with an embodiment of the invention. While serving apparatus 500 is depicted in the cooling mode, apparatus 500 may be used to heat aluminum plate 501 (which functions as the serving surface on which an item is placed) based on the previous discussion.

Peltier device 502 is thermally coupled to serving surface 501 and copper block 504, where the top side (corresponding to ceramic layer 312 as shown in FIG. 3) is physically situated against serving surface 501 and the bottom side (corresponding to ceramic layer 313) is physically situated against copper block 504. Thermal conductivity may be enhanced by ensuring the flatness of the installation surface, and coating the contact surface with a thin layer of heat conduction silicon grease. Also, in order to avoid fracturing the ceramic layers of Peltier device 502, the pressure against the layers should be even and not excessive when fixing device 502.

Heat pipe 503 is thermally coupled to Peltier device 502 through copper block 504 so that heat flows along heat flow 509 a and 509 b. However, with some embodiments, heat pipe 503 may be directly placed against Peltier device 502. Heat pipe 502 transports heat along heat flow 509 b by traversing through copper block 504 via branches 507 a-507 c and heat sink 505. Heat is thus transported along heat flow 509 c and into the surrounding environment of serving apparatus 500.

With some embodiments, heat sink 505 may be constructed from copper and/or aluminum in order to achieve performance, size, and cost objectives.

With some embodiments, fan 506 operates when apparatus is operating in the cooling mode. However, with some embodiments, fan 506 may operate in the heating and/or cooling modes. Fan 506 assists in the transfer of heat by drawing in cool air 510 a and 510 b so that heat sink 505 may be kept to a smaller size than without fan 506. With some embodiments, the speed of fan 506 may be changed based on the temperature of serving surface 501. For example, the speed may be increased when the difference of measured temperature of serving surface 501 and the desired temperature increases. However, with some embodiments, the speed of fan 506 may be fixed when fan 506 is activated and may operate during the entire duration of operation.

With some embodiments, while not explicitly shown in FIG. 5, a cooling fan may circulate air to provide inner air convection within the serving chamber (within serving cover 508 and serving plate 501) to enhance the cooling of food within the chamber. With some embodiments, a fan may support inner air convection when the apparatus is operating in the heating mode.

FIG. 6 shows control device 600 for controlling apparatus 100 (corresponding to control device 108 as shown in FIG. 1), apparatus 200 (corresponding to control device 208 as shown in FIG. 2), and apparatus 500 (as shown in FIG. 5) in accordance with an embodiment of the invention. Processing system 601 may execute computer executable instructions from a computer-readable medium (e.g., storage device 604) in order provide verify communication redundancy for a network, Memory 602 is typically used for temporary storage while storage device 504 may comprise a flash memory and/or hard drive for storing computer executable instructions and a profile image. However, computer storage media may include volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer storage media include, but may not be limited to, random access memory (RAM), read only memory (ROM), electronically erasable programmable read only memory (EEPROM), flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and that can be accessed by processing system 601. The executable instructions may carry out any or all of the method steps described herein.

With some embodiments, processing system 601 may correspond to one or more processors and storage device 604 may correspond to one or more memories.

Control device 600 may be implemented as one or more ASICs or other integrated circuits (e.g., a single chip computer) having instructions for performing operations as described in connection with one or more of any of the embodiments described herein. Said instructions may be software and/or firmware instructions stored in a machine-readable medium and/or may be hard-coded as a series of logic gates and/or state machine circuits in one or more integrated circuits and/or in one or more integrated circuits in combination with other circuit elements.

With some embodiments, control device 600 supports different control capabilities for heating and/or cooling. For example, device 600 may obtain a temperature setting (desired temperature) from a user through an input device and control one or more Peltier devices (e.g., Peltier devices 802-805 as shown in FIG. 8) to compensate for environmental factors in order to approximate the desired temperature. Control device 600 may also sense when cover 508 (as shown in FIG. 5) is open (e.g. through a switch not explicitly shown), and control the Peltier devices accordingly. For example, control device 600 may activate the Peltier devices for a longer period of time when cover 508 is open than when it is shut.

FIG. 7 shows circuitry 700 for controlling Peltier devices in accordance with an embodiment of the invention. While some of the functionality of a serving apparatus may be implemented with a control device (e.g., control device 600 as shown in FIG. 6), some or all of the functionalities ma y be implemented with sepa rate circuitry, e.g., circuitry 700. For example, circuitry 700 controls the activation of the Peltier devices by a comparator 701 comparing temperature setting 704 and measured temperature 703. Comparator 701 may have hysteresis characteristics so that once Peltier device 706 is activated by providing electrical power from source 705 through power switch 702, activation continues until the serving surface reaches a hysteresis temperature.

FIG. 8 shows a collection of Peltier devices for changing a serving surface temperature in accordance with an embodiment of the invention. Embodiments may support one or more Peltier devices in order to increase or decrease the temperature of a serving surface. With some embodiments, as shown in FIG. 8, four Peltier devices 802-805 may heat or cool serving surface 801. Some or all of the Peltier devices may be activated at one time. For example, when the temperature of serving surface 801 is within a temperature range, Peltier devices 802-805 may be deactivated. When the measured temperature of serving surface 801 is outside the temperature range, all of the Peltier devices 802-805 are activated. (This approach is incorporated in flowchart 1100 as shown in FIG. 11 and will be further discussed.) However, with some embodiments, only a proper subset of Peltier devices (e.g., devices 802 and 805 or devices 803 and 804) is activated at a given time when the temperature is outside the temperature range. Moreover, different subsets may be activated in a sequenced manner in order to provide more consistent thermal properties, such as more even cooling and/or heating, over serving surface 801. For example, a first subset and a second subset may be activated and deactivated, respectively, during a first time duration while reversing activation states during the second time duration.

Some embodiments may support a greater number of Peltier devices. However, the number of Peltier devices may be limited by physical constraints and/or electrical power limitations. FIG. 9 shows a collection of sixteen Peltier devices 902-917 for changing serving surface 901 in accordance with an embodiment of the invention. As discussed previously, some or all of devices 902-917 may be activated at the same time. Devices 902-917 may be partitioned into a plurality subsets, e.g., a first subset including devices 802, 805, 807, 808, 811, 812, 814, and 817, a second subset including 802, 804, 807, 809, 810, 812, 815, and 817, and third subset including devices 803, 805, 806, 808, 811, 813, 814, and 816, where some or all of the subsets may have overlapping members.

With some embodiments, the same Peltier devices may be used for different modes of operation. For example, referring to FIG. 8, Peltier devices 802-805 may be used both for heating and cooling.

With some embodiments, different Peltier devices may be used for different modes of operation. For example, Peltier devices 802 and 805 may be used for cooling while Peltier devices 803 and 804 may be used for heating. As another example, Peltier devices 802-805 may be used for cooling while only Peltier devices 502 and 805 are used for heating.

FIG. 10 shows flowchart 1000 for controlling a serving apparatus in accordance with an embodiment. At block 1001, a control device (e.g., control device 108 as shown in FIG. 1) reads the measured temperature of the serving surface (e.g., surface 101) from the temperature sensor (e.g., sensor 109). At block 1002, the control device determines whether to activate some or all of the Peltier devices at block 1003. With some embodiments, selected Peltier devices (i.e., all or some of the Peltier devices) may be activated until the measured temperature reaches a hysteresis temperature so that a hysteresis characteristic is incorporated. For example, the temperature setting may be 35° F. when the serving apparatus is operating in the cooling mode. In such a case, the selected Peltier devices may be activated until the serving surface is cooled down sufficiently so that the measured temperature reaches 33° F. (the hysteresis temperature). The hysteresis temperature is typically offset from the temperature setting by several degrees so that control cycling is reduced. Different exemplary procedures for controlling the Peltier devices will be discussed in FIGS. 11 and 12.

At block 1004, the control device determines whether to activate one or more fans (e.g., fans 114 and 115). For example, with some embodiments the fans may be activated at block 1005 only when the measured temperature is outside a temperature range to assist transferring heat with the environment of the serving apparatus. However, with some embodiments, a fan may be activated only for specific operating modes, e.g., a cooling mode or a heating mode.

FIG. 11 shows flowchart 1100 for controlling Peltier devices in accordance with an embodiment. At block 1101 a control device obtains a measured temperature of a serving surface from a temperature sensor and the temperature setting (desired temperature) of the serving surface from a user input. At block 1102, the control device determines the mode of operation, i.e., cooling or heating. Based on the mode of operation, the control device determines whether to activate the Peltier devices based on the measured temperature, temperature setting, and hysteresis temperature at blocks 1103-1108.

At block 1103, the control device operates in the cooling mode and determines whether the measured temperature exceeds the cooling temperature setting. If so, the control device activates the Peltier devices until the measured temperature is less than or equal to the cooling hysteresis temperature at block 1104. Otherwise (i.e., the measured temperature does not exceed the cooling temperature setting), the control device deactivates the Peltier devices at block 1105.

At block 1106, the control device operates in the heating mode and determines whether the measured temperature is less than the heating temperature setting. If so, the control device activates the Peltier devices until the measured temperature is greater than or equal to the heating hysteresis temperature at block 1107. Otherwise (i.e., the measured temperature does not exceed the cooling temperature setting), the control device deactivates the Peltier devices at block 1108.

FIG. 12 shows flowchart 1200 for controlling Peltier devices in accordance with an embodiment. Flowchart 1200 is similar to flowchart 1100, where blocks 1201 and 1202 correspond to blocks 1101 and 1102, respectively. However, process 1200 activates all of the Peltier devices when the measured temperature is outside a temperature range (e.g., between the temperature setting and the hysteresis temperature) at blocks 1204 and 1207 and a selected subset of the Peltier devices when the measured temperature is within the temperature range at blocks 1205 and 1208. When operating at blocks 1205 and 1208, the control device may select different subsets from the plurality of Peltier devices and sequence through the different subsets. For example, referring to FIG. 9, the control device may first select and activate the first subset for a first time duration, followed by the second subset, followed by the third subset, followed by the first subset, and so forth.

As can be appreciated by one skilled in the art, a computer system with an associated computer-readable medium containing instructions for controlling the computer system may be utilized to implement the exemplary embodiments that are disclosed herein. The computer system may include at least one computer such as a microprocessor, digital signal processor, and associated peripheral electronic circuitry.

While the invention has been described with respect to specific examples including presently preferred modes of carrying out the invention, those skilled in the art will appreciate that there are numerous variations and permutations of the above described systems and techniques that fall within the spirit and scope of the invention as set forth in the appended claims. 

We claim:
 1. An apparatus for changing a measured temperature of a serving surface, the apparatus comprising: a first Peltier device transferring heat between a top side and a bottom side of the first Peltier device; the serving surface thermally coupled with the top side of the first Peltier device; a heat pipe comprising a first portion and a second portion, the first portion thermally coupled with the bottom side of the first Peltier device, the heat pipe transferring the heat with the bottom side of the first Peltier device, the heat flowing between the first portion and the second portion; and a heat exchange device thermally coupled to the second portion of the heat pipe to exchange the heat with the second portion.
 2. The apparatus of claim 1, wherein: the serving surface is thermally coupled to the top side of the first Peltier device to decrease the measured temperature; the heat pipe extracting the heat from the bottom side of the first Peltier device, the heat flowing from the first portion to the second portion; and the heat exchange device thermally coupled to the second portion of the heat pipe to extract the heat from the second portion.
 3. The apparatus of claim 1, wherein: the serving surface is thermally coupled to the top side of the first Peltier device to increase the measured temperature; the heat pipe transferring the heat to the bottom side of the first Peltier device, the heat flowing from the second portion to the first portion; and the heat exchange device thermally coupled to the second portion of the heat pipe to transfer the heat to the second portion.
 4. The apparatus of claim 1, further comprising a plurality of Peltier devices.
 5. The apparatus of claim 4, further comprising: a temperature sensor providing an indication of the measure temperature of the serving surface; and a control device activating selected Peltier devices from the plurality of Peltier devices based on the indication.
 6. The apparatus of claim 5, wherein the control device selects different Peltier devices to activate from the plurality of Peltier devices.
 7. The apparatus of claim 5, wherein the control device activates all of the plurality of Peltier devices when the measured temperature is outside a temperature range.
 8. The apparatus of claim 7, wherein the temperature range is between a temperature setting and a hysteresis temperature.
 9. The apparatus of claim 7, wherein the control device activates a first proper subset of the plurality of Peltier devices when the measured temperature is within the temperature range.
 10. The apparatus of claim 9, wherein the control device deactivates all of the plurality of Peltier devices when the measured temperature reaches a hysteresis temperature.
 11. The apparatus of claim 9 wherein the control device activates a second proper subset during a subsequent time interval.
 12. The apparatus of claim 5 further comprising: a fan; and the control device varying a speed of the fan based on the measured temperature.
 13. The apparatus of claim 5, wherein the control device changes polarity of electrical power to the plurality of Peltier devices to change a mode of operation of the apparatus.
 14. The apparatus of claim 13, further comprising: a fan; and the control device activating the fan based on the mode of operation.
 15. A method for controlling a measured temperature of a serving surface, the method comprising: transporting heat between the a top side and a bottom side of a first Peltier device that is thermally coupled with the serving surface; transferring the heat between the bottom side of the first Peltier device and a first portion of a heat pipe that is thermally coupled with the bottom side of the first Peltier device; moving the heat between the first portion and a second portion of the heat pipe; and exchanging the heat between the second portion of the heat pipe and a heat exchange device that is thermally coupled with the second portion.
 16. The method of claim 15, wherein: the transporting comprises transporting the heat from the top side to the bottom side of the first Peltier device to decrease the measured temperature; the transferring comprises transferring the heat from the bottom side of the first Peltier device to the first portion of the heat pipe; the moving comprises moving the heat from the first portion to the second portion of the heat pipe; and the exchanging comprises exchanging the heat from the second portion of the heat pipe to the heat exchange device.
 17. The method of claim 15, wherein: the transporting comprises transporting the heat from the bottom side to the top side of the first Peltier device to increase the measured temperature; the transferring comprises transferring the heat from the first potion of the heat pipe to the bottom side of the first Peltier device; the moving comprises moving the heat from the second portion to the first portion of the heat pipe; and the exchanging comprises exchanging the heat from the heat exchange device to the second portion of the heat pipe.
 18. The method of claim 15, further comprising: activating selected Peltier devices from a plurality of Peltier devices based on the measured temperature of the serving surface, wherein the plurality of Peltier devices includes the first Peltier device.
 19. The method of claim 18, further comprising: selecting different Peltier devices from the plurality of Peltier devices.
 20. The method of claim 18, further comprising: activating all of the plurality of Peltier devices when the measured temperature is outside a temperature range.
 21. The method of claim 20, further comprising: activating a proper subset of the plurality of Peltier devices when the measured temperature is within the temperature range.
 22. The method of claim 21, further comprising: deactivating all of the plurality of Peltier devices when the measured temperature reaches a hysteresis temperature.
 23. A non-transitory computer-readable storage medium storing computer-executable instructions that, when executed, cause at least one processor to perform operations comprising: measuring a measured temperature of a serving surface; and activating selected Peltier devices from a plurality of Peltier devices based on the measured surface temperature.
 24. The computer-readable medium of claim 23, wherein the computer-executable instructions, when executed, cause the at least one processor to perform: selecting different Peltier devices from the plurality of Peltier devices.
 25. The computer-readable medium of claim 24, wherein the computer-executable instructions, when executed, cause the at least one processor to perform: activating all of the plurality of Peltier devices when the measured temperature is outside a temperature range.
 26. The computer-readable medium of claim 25, wherein the computer-executable instructions, when executed, cause the at least one processor to perform: activating a proper subset of the plurality of Peltier devices when the measured temperature is within the temperature range.
 27. The computer-readable medium of claim 26, wherein the computer-executable instructions, when executed, cause the at least one processor to perform: deactivating all of the plurality of Peltier devices when the measured temperature reaches a hysteresis temperature. 